Brush holder



May 27, 1 924. :,49s,2o3

P. ROBERG BRUSH HOLDER Filed July 11. 1923 gwuentot:

Patented May 27, 1924.

UNITED STATES PATENT OFFICE.

PHILIP ROBERG, OF BROOKLYN, NEVJ YORK, ASSIGNOR' TO UNION CARBIDE & CAR-EON RESEARCH LABORATORIES, INC.,

A. CORPORATION OF NEYV YORK.

BRUSH HOLDER.

Application filed July 11,

To all iii/10m it may concern-.-

Be it known that I, PHILIP Romano, a a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Brush Holders, of which the following is a specification.

This invention relates to an improved brush-holder for supporting a carbon or similar brush against a commutator to obtain satisfactory commutation under varying conditions of commutator surface, temperature and vibration.

Unsatisfactory commutation often occurs owing to the displacement of the brush by the expansion or contraction of the brushholder rigging, by the unevenness of the commutator and brush surface, and by excessive vibration. In brush-holder riggings, as heretofore constructed, the brush may be supported in a satisfactory commutating position under a given condition of temperature, but when the ma chine temperature rises, for example, the differential expansion between the rigging and frame moves the brush so that its leading edge will be raised slightly off of the commutator surface and only the trailing portion will bear on the commutator or vice versa, tending to wear in a new brush contacting surface. In the meantime, however. more or less injurious sparking occurs until the brush face again becomes practically concentric to the commutator. Similarly. when the brush rigging again cools off, due either to changes in external temperature, to a decrease in load, or to a shut down, the brush face will again be displaced from the commutator surface and there will be wear of the opposite edge of the brush and renewed sparking until the brush face again becomes adjusted to a practically concentric position relative to the commutator surface. These temperature alternations may be so frequent as to entirely prevent permanent bedding of the brush.

Present type brush mountings also to a greater or lesser degree impede satisfactory commutation because they do not constantly adjustthe brush face to commutator irregularities due to such causes as uneven wear of the commutator bars or their displacement by the differential expansion of the copper and mica. Simple pivoted type brush-holders are impractical because of the 1923. Serial No. 650,934.

fact that the brush. being free to make slight rotational adjustments, is also free to gradually rotate and lose its original position as the result of unbalanced wear between the leading and trailing edges. Moreover. where there are jars or excessive vi bration, as on an automobile, the brush face may be permanently displaced from commutating position by rotation about its pivot from its normal operating position.

lVhile permittingslight continuous adjustments of the brush face to meet changing operating conditions, the brush-holders should also tend to maintain the longitu: dinal or radial brush axis in the same general position relatively to the commutator and provide a stabilizing moment which will automa cally regulate the wear of the brush race to this end. Furthermore, the holder should prevent any permanent dislocation of the brush face relatively to the commutator surface. Accordingly, the principal object of this invention is to provide an improved brush'holder by means of which the brush surface shall be automatically adjustable to always present substantially its full face to the commutator surface regardless of temperature variations, wear and jars or excessive vibration.

Broadly, the essential feature of this invention comprises a brush-holdcr capable of free pivotal adjustments and provided with a cooperating means which appliesthereto forces tending to maintain the brush in the desired equilibrium position or to gradually restore it to that position. Normally, the brush is pivotally supported in stable equilibrium and its operating position, with its contacting face free to make slight automatic adjustments so that full engagementwith the commutator is continuously maintained, and a cooperating means is provided which restrains excessive tilting of the brush, and at all times tends to restore the brush to the desired position of stable equilibrium and maintain a constant average rate of brush wear at the leading and trailing edges. The above and other objects and the novel features of this invention will. be apparent from the following description taken with the accompanying drawings, in which- Figs. 1 and 2 are side and rear views illustrating a brush-holder embodying this invention, and

Figs. and 4; are side and rear views illustrating another brush-holder embodying this invention.

As shown, the improved brush-holder comprises a fixed supporting bracket S which may be secured to stationary part of an electric machine having a commutator H. A brush mounted in the usual manner on this bracket is displaced from its full contacting position as the dimensions of this bracket are changed by temperature variations which produce a dilferential expansion or contraction of the bracket relatively to the machine upon which it is'mounted. According to the present invention displacements caused by temperature changes, will compensate for wear and any irregularities present in the commutator surface, and also prevent a complete dislocation of the brush face by excessive vibration. To this end, the brush B is pivotally supported on the bracket on an axis parallel to the working surface of the commutator and suitable spring means may be employed to maintain the brush axis in the same general position and to resist abnormal tilting of the brush and restore it to its normal. position.

In the desirable embodiment of the invention shown in Figs. 1 and 2 the brush is freely slidable but not tiltable in a guide or supportsuch as a brush-holder box P, which is pivoted on the bracket S, as by trunnion pins A thereon which project through holes in spaced arms S of the bracket, whereby the box P and the brush therein are pivotally supported as a unit on an axis passing through the brush, and the brush may at the same time be fed toward the commutator as it wears. Suitable means such as a yield-able finger J having an adjustable tension spring F, may engage the outer end of the brush and press it against the commutator. The point of application of the pressure of the finger J may be such that it will not nor mally produce a turning moment of the box P and brush B about their pivot. The supporting axis of the brush-holder box P is desirably parallel to the working surface of ,the commutator and may be disposed between the latter and the center of gravit of the brush-holder box and brush combined.

In order to limit the tilting of the brushholder box and the brush about their axis in either direction and to maintain the brush in a position of stable equilibrium relative to the commutator surface, a suitable restrain and restoring means is provided. As

illustrated in Fig. 1, a leaf spring D may be employed having one end secured to the pivoted box P, as by securing it to a collar C that is fastened to a pivot pin A by a set screw K. The movement of the other end of spring D may be limited, as by inserting it between the fixed abutments E and E on the supporting bracket S, the abutment E being adjustable to vary the position of the spring for the initial setting of the brushholder box P. By loosening the screw K, the box P may also be initially set in any angular position relatively to the spring D.

lVhen the bracket S expands, the box P and the brush carried by it will be free to tilt slightly about their supporting axis to allow the curved face of the brush to maintain full contact with the commutator surface, since the spring does not ofier a material resistance to slight tilting to compensate for minor displacements such as are produced by temperature changes, irregularities of the commutator surface and unbalanced wear caused by the frictional pull on the brush face and the unbalanced weight of the brush and holder. The spring D, when bent slightly from its normal position to compensate for a differential increase in the dimensions of the bracket S, will act to restore the brush to its normal running position when the temperature decreases, thereby maintaining the contacting face of the brush in full engagement with the commutator during all changes in temperature. Likewise, the pivoted brush is free to follow irregularities of the commutator surface, the spring D serving to prevent total displacement or dislocation of the brush by rotation about its pivot, particularly when the brush is subjected to excessive vibration or jar, as may be the case in an automobile generator brush. lVhen the brush support tilts in either direction from its normal position, the spring D increasingly resists further movement and at all times tends to re- Hit) tore the support and brush to their normal position.

Figs. 3 and 4 illustrate another embodiment of the invention in which the brushholder box P is pivotally mounted on a bracket S as in Figs. 1 and 2. In this arrangement the spring D and its associated parts are eliminated and a spring J serves the double purpose of applying pressure to hold the brush against the commutator and to maintain the brush-holder box and brush in equilibrium. The rear end of the brush B may be flat but is desirably provided with oppositely inclined cam sur faces forming a recess G to receive a roller R carried by the spring J. When the bruslnholder P and the brush B tilt in either direction, the camming action of the spring pressed roller R against rear end of the brush or the inclined surfaces of recess G- will tend to restore the brushholder and brush to normal position as temperature variations change the dimensions of the bracket S and associated parts.

It will be seen that the spring means for resisting the tilting of the brush has a threefold function, (1) it may be set so as to balance the Weight of the brush-holder box with or without the brush therein; (2) it acts to maintain the angle between the brush face and the length of the brush practic-ally constant and prevents excessive wear of the heel of the brush and consequent brush rotation, by balancing the moment of the force of friction about the pivotal axis by its own opposite moment about this axis; and (3) it prevents the brush from being rotated permanently out of its position of stable equilibrium by excessive vibrations or ars.

It will be apparent from the foregoing that the brush is so mounted that it has alimited freedom of movement on its pivot whereby a maximum area of contact between the brush and commutator will be maintained during relative displacen'ients of the brush and commutator surfaces by expansion and contraction of the brush rigging and by unevenness of the commutator surface.

I claim:

1. A brush-holder comprising the combination with a pivoted brush support, of means resisting the tilting of said support in either direction about its pivot and tending to retain the same in stable equilibrium relatively to a commutator surface.

2. A brush-holder comprising the combination with apivoted brush support adapted to tilt slightly to adjust a brush face for changing operating conditions, of means adapted to maintain the longitudinal axis of such brush in the same general position and prevent a permanent dislocation of the brush face relatively to a commutator surface.

3. A brush-holder comprising the combination of a pivoted brush support adapted to tilt slightly in either direction to automatically adjust a brush face relatively to a commutator surface in accordance with changing operating conditions, and spring means cooperating with said support to maintain the longitudinal axis of such brush in the same general position and prevent a permanent dislocation of the brush face relatively to the commutator surface. 4;. The combination with a commutator,

of a brush bearing against the same and pivoted on an axis parallel to the commutator surface, and means tending to retain said brush in stable equilibrium relatively to the commutator and yieldingly resisting its movement about said axis.

5. The combination with a pivoted brush support, of a brush slidably mounted thereon, and spring means adapted to slide said brush relatively to said support and yieldingly resisting the tilting of said support about its axis.

6. A brush-holder comprising the combination of a stationary bracket, a brush support pivotally mounted thereon, and spring means adapted to slide a brush relatively to said support and yieldingly resisting the tilting of said support in either direction about said axis.

7. A brush-holder comprising a pivoted member adapted to slidably support a. brush, means comprising a spring adapted to slide such brush relatively to said member, and another spring cooperating with said member to permit the latter to tilt slightly in either direction but preventing a permanent dislocation of the brush face relatively to the commutator surface.

8. The combination with a commutator, of a brush bearing against the same, a brush holding member slidably supporting said brush, a stationary bracket pivotally supporting said member on an axis passing through said brush parallel to the working surface of said commutator, and a spring limiting the tilting of said member in either direction about its pivot and tending to retain it in its normal operating position.

9. The combination with a. stationary bracket, of a brush support pivoted thereon, a brush slidably mounted on said support, and means yieldingly bearing against said brush and cooperating therewith to resist the tilting of said support and brush and tending to retain the latter in its normal operating position.

In testimony whereof, I affix my signa ture.

PHILIP ROBERG. 

